What did the alpha particles that passed straight through the foil reveal about atoms?
Atoms are mostly empty space.
AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Foundation · 5.1.1.3
Revise AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Foundation specification point 5.1.1.3, The development of the model of the atom (common content with physics), with free active-recall flashcards. Flip through the set or review every question and answer below.
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What did the alpha particles that passed straight through the foil reveal about atoms?
Atoms are mostly empty space.
What did the large-angle deflections and occasional bounce-backs of alpha particles reveal about atoms?
Most of an atom’s mass and all its positive charge are concentrated in a tiny central region.
What is the structure of an atom in the nuclear model?
A small, dense, positively charged nucleus sits at the centre, with electrons outside it.
How do the nuclear and plum pudding models differ in their distribution of positive charge?
The nuclear model concentrates it in the nucleus; the plum pudding model spreads it throughout the atom.
How were atoms pictured before the discovery of electrons?
As tiny, solid spheres that could not be divided.
Why did the discovery of the electron require the earlier model of the atom to change?
It showed that atoms contain smaller parts.
How does the plum pudding model describe an atom?
A sphere of positive charge, spread throughout the atom, with negative electrons embedded in it.
How did Bohr’s model change the picture of where electrons orbit the nucleus?
Electrons occupy specific orbits or shells at fixed distances from the nucleus, rather than orbiting at any random distance.
What feature of the earlier nuclear model did Bohr retain?
A small central nucleus.
Why was Bohr’s model accepted as better than the earlier nuclear model alone?
Bohr’s calculations agreed with experimental observations.
How is the positive charge of a nucleus related to protons?
It is a whole number of equal positive charges, each associated with a proton.
What is a neutron?
An uncharged particle within the nucleus.
Whose experimental work provided evidence for neutrons?
James Chadwick’s.
When did evidence for neutrons appear relative to the acceptance of the nucleus?
About 20 years after the nucleus became an accepted scientific idea.